From: Johannes Weiner <hannes@cmpxchg.org> To: Yafang Shao <laoar.shao@gmail.com> Cc: linux-fsdevel@vger.kernel.org, Linux MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>, Dave Chinner <david@fromorbit.com>, Michal Hocko <mhocko@suse.com>, Roman Gushchin <guro@fb.com>, Andrew Morton <akpm@linux-foundation.org>, Linus Torvalds <torvalds@linux-foundation.org>, Al Viro <viro@zeniv.linux.org.uk>, Kernel Team <kernel-team@fb.com> Subject: Re: [PATCH] vfs: keep inodes with page cache off the inode shrinker LRU Date: Wed, 12 Feb 2020 11:42:35 -0500 Message-ID: <20200212164235.GB180867@cmpxchg.org> (raw) In-Reply-To: <CALOAHbC3Bx3E7fwt35zuiHfuC8YyhVWA1tDh2KP+gQJoMtED3w@mail.gmail.com> On Wed, Feb 12, 2020 at 08:25:45PM +0800, Yafang Shao wrote: > On Wed, Feb 12, 2020 at 1:55 AM Johannes Weiner <hannes@cmpxchg.org> wrote: > > Another variant of this problem was recently observed, where the > > kernel violates cgroups' memory.low protection settings and reclaims > > page cache way beyond the configured thresholds. It was followed by a > > proposal of a modified form of the reverted commit above, that > > implements memory.low-sensitive shrinker skipping over populated > > inodes on the LRU [1]. However, this proposal continues to run the > > risk of attracting disproportionate reclaim pressure to a pool of > > still-used inodes, > > Hi Johannes, > > If you really think that is a risk, what about bellow additional patch > to fix this risk ? > > diff --git a/fs/inode.c b/fs/inode.c > index 80dddbc..61862d9 100644 > --- a/fs/inode.c > +++ b/fs/inode.c > @@ -760,7 +760,7 @@ static bool memcg_can_reclaim_inode(struct inode *inode, > goto out; > > cgroup_size = mem_cgroup_size(memcg); > - if (inode->i_data.nrpages + protection >= cgroup_size) > + if (inode->i_data.nrpages) > reclaimable = false; > > out: > > With this additional patch, we skip all inodes in this memcg until all > its page cache pages are reclaimed. Well that's something we've tried and had to revert because it caused issues in slab reclaim. See the History part of my changelog. > > while not addressing the more generic reclaim > > inversion problem outside of a very specific cgroup application. > > > > But I have a different understanding. This method works like a > knob. If you really care about your workingset (data), you should > turn it on (i.e. by using memcg protection to protect them), while > if you don't care about your workingset (data) then you'd better > turn it off. That would be more flexible. Regaring your case in the > commit log, why not protect your linux git tree with memcg > protection ? I can't imagine a scenario where I *wouldn't* care about my workingset, though. Why should it be opt-in, not the default?
next prev parent reply index Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-02-11 17:55 Johannes Weiner 2020-02-11 18:20 ` Johannes Weiner 2020-02-11 19:05 ` Rik van Riel 2020-02-11 19:31 ` Johannes Weiner 2020-02-11 23:44 ` Andrew Morton 2020-02-12 0:28 ` Linus Torvalds 2020-02-12 0:47 ` Andrew Morton 2020-02-12 1:03 ` Linus Torvalds 2020-02-12 8:50 ` Russell King - ARM Linux admin 2020-02-13 9:50 ` Lucas Stach 2020-02-13 16:52 ` Arnd Bergmann 2020-02-15 11:25 ` Geert Uytterhoeven 2020-02-15 16:59 ` Arnd Bergmann 2020-02-16 9:44 ` Geert Uytterhoeven 2020-02-16 19:54 ` Chris Paterson 2020-02-16 20:38 ` Arnd Bergmann 2020-02-20 14:35 ` Chris Paterson 2020-02-26 18:04 ` santosh.shilimkar 2020-02-26 21:01 ` Arnd Bergmann 2020-02-26 21:11 ` santosh.shilimkar 2020-03-06 20:34 ` Nishanth Menon 2020-03-07 1:08 ` santosh.shilimkar 2020-03-08 10:58 ` Arnd Bergmann 2020-03-08 14:19 ` Russell King - ARM Linux admin 2020-03-09 13:33 ` Arnd Bergmann 2020-03-09 14:04 ` Russell King - ARM Linux admin 2020-03-09 15:04 ` Arnd Bergmann 2020-03-10 9:16 ` Michal Hocko 2020-03-09 15:59 ` Catalin Marinas 2020-03-09 16:09 ` Russell King - ARM Linux admin 2020-03-09 16:57 ` Catalin Marinas 2020-03-09 19:46 ` Arnd Bergmann 2020-03-11 14:29 ` Catalin Marinas 2020-03-11 16:59 ` Arnd Bergmann 2020-03-11 17:26 ` Catalin Marinas 2020-03-11 22:21 ` Arnd Bergmann 2020-02-12 3:58 ` Matthew Wilcox 2020-02-12 8:09 ` Michal Hocko 2020-02-17 13:31 ` Pavel Machek 2020-02-12 16:35 ` Johannes Weiner 2020-02-12 18:26 ` Andrew Morton 2020-02-12 18:52 ` Johannes Weiner 2020-02-12 12:25 ` Yafang Shao 2020-02-12 16:42 ` Johannes Weiner [this message] 2020-02-13 1:47 ` Yafang Shao 2020-02-13 13:46 ` Johannes Weiner 2020-02-14 2:02 ` Yafang Shao 2020-02-13 18:34 ` [PATCH v2] " Johannes Weiner 2020-02-14 16:53 ` [PATCH] " kbuild test robot 2020-02-14 21:30 ` kbuild test robot 2020-02-14 21:30 ` [PATCH] vfs: fix boolreturn.cocci warnings kbuild test robot 2020-05-12 21:29 ` [PATCH] vfs: keep inodes with page cache off the inode shrinker LRU Johannes Weiner 2020-05-13 1:32 ` Yafang Shao 2020-05-13 13:00 ` Johannes Weiner 2020-05-13 21:15 ` Andrew Morton 2020-05-14 11:27 ` Johannes Weiner 2020-05-14 2:24 ` Andrew Morton 2020-05-14 10:37 ` Johannes Weiner
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